Exposure control systems for single reflex cameras having a detachable housing

ABSTRACT

In a single lens reflex camera, an exposure control system for a photographic camera is so constructed that a housing having a pentagonal prism therein is attachable to and detachable from the camera body. A detecting circuit for detecting the brightness of an object through the objective lens in an exposure control circuit and a memory circuit are built-in to the housing and a portion of the circuitry thereof is made as an integrated circuit. In the camera body a portion of the switching circuit for controlling the exposure of an electric shutter using the output of the detecting circuit as one input is built-in as an integrated circuit. The mounting of the pentagonal prism housing onto the camera body causes the terminals of the detecting and memory circuit and the terminals of the switching circuit to connect with one another.

United States Patent 1191 Yata [ 1 3,733,984 1 51 May 22,1973

[54] EXPOSURE CONTROL SYSTEMS FOR SINGLE REFLEX CAMERAS HAVING ADETACHABLE HOUSING [75] Inventor: Kotaro Yata, Ikeda, Japan [73]Assignee: Minolta Camera Kabushiki Kaisha,

Osaka-shi, Osaka-fu, Japan [22] Filed: July 3, 1972 [21] Appl. No.:268,375

52 U.S. Cl ..95 10 (31*, 95/42 51 Int. Cl. ..G03b 7/08, G03b 19/12 58Field of Search ..95/10 0, 10 CT, 10 PD, 95/42 [56] References CitedUNITED STATES PATENTS 3,630,133 12/1971 Shimomura .35 42 3,635,1361/1912 11011 et al ..95/42 x 3,643,560 2/1972 Bonk ..95/42 x PrimaryExaminer-Samuel S. Matthews Assistant Examiner-Michael L. GellnerAttorney-Watson, Cole, Grindle & Watson [57] ABSTRACT In a single lensreflex camera, an exposure control system for a photographic camera isso constructed that a housing having a pentagonal prism therein isattachable to and detachable from the camera body. A detecting circuitfor detecting the brightness of an object through the objective lens inan exposure control circuit and a memory circuit are built-in to thehousing and a portion of the circuitry thereof is made as an integratedcircuit. In the camera body a portion of the switching circuit forcontrolling the exposure of an electric shutter using the output of thedetecting circuit as one input is built-in as an integrated circuit. Themounting of the pentagonal prism housing onto the camera body causes theterminals of the detecting and memory circuit and the terminals of theswitching circuit to connect with one another.

5 Claims, 9 Drawing Figures SHEET 1 [1F 4 F I G. I

DETECTING 8: MEMORY CIRCUIT PAH-M W22 ma INTEGRATED CIRCUIT L MG W 0 CNH mmfl T C RCU Y E ETC AC R FIR \[LRRR W E EIOO.

DS DC C m T WW E G MVW L A os E M YEW Uml

i AS U W EC A mm MHTC F I G. 9

a INTEGRATED POWER SOURCE CIRCUIT FOR SWITCHING CIRCUIT PATENI msrzmavaSHEET 2 UP 4 D5 'Ds FiG. 2

PATENT xzz I975 733 ,9 4

SHEET 3 [IF 4 POTENTIAL AT POINT a 0 LOGARITHM OF THE ILLU- MINANCE ONTHE LIGHT RECEIVING ELEMENT PATENTEW v Q 3,733,984

SHEET u or 4 S2 START osmon 28 OF FRONT EDGE OF REAR CURTAIN Sr STARTPOSITION OF REAR EDGE 0 t t t 1 OF FRONT CURTAIN BACKGROUND OF THEINVENTION:

The present invention relates to an exposure control system in a singlelens reflex camera and, more particularly, relates to an exposurecontrol system in a single lens'reflex camera which receives theincident scene light passing through the objective lens to detect thebrightness of an object and electrically controls the shutter speed.

In a photographic camera, it is well known to detect the brightness ofan object and control the exposure by operating a switching circuit bymeans of the light detected output. It is also well known to measure thescene light passing through the objective lens by a light receivingelement to determine the brightness by the signal output thereof of anobject and to store the signal output in a capacitor. The exposure iscontrolled by inputting the stored voltage into the switching circuitsimultaneously with the starting of the exposure. And, according tosucha system, in order to enlarge the controllable range of thebrightness of an object, because the signal output stored in thecapacitor is logarithmically compressed, a circuit is required toprovide a logarithmic expansion to the voltage of the memory capacitorfor controlling the exposure. Additional compensating circuits arerequired for respectively compensating the voltage fluctuation of thepower source in the detecting circuit, the switching circuit, andassociated circuits thereof, which results in a huge circuit.

Therefore, when the related structures in these circuits are arranged inone integrated circuit, the terminals of the integrated circuit packageare numerous. When suchan integrated circuit is built into a camera, thecapacity of the camera must be increased and accordingly a large spaceis necessary for connecting those tenninals to the terminals of thenon-integrated circuitry and it is difficult to wire and assemble. Thisfact is a disadvantage in making the circuit system an integratedcircuit.

THE OBJECT OF THE INVENTION One object of the present invention is toprovide an exposure control system in which that circuitry capable ofbeing integrated is constructed as integrated circuits for detectingreceived light passing through an objective lens and controlling theexposure time of a single lens reflex camera in accordance with thedetected output.

Another object of the present invention is to provide an improved cameraof the type specified with integrated electric circuits incorporated inthe camera while maintaining normal camera size, and which camera iseasy to assemble and handle and is also economical.

A further object of the present invention is to provide an exposurecontrol system, wherein a pentagonal prism, a light receiving elementfor receiving the scene light passing through the'objective lens, and.an integrated circuit for detecting and storing the current generated bythe light receiving element are built-in a detachable housing; and thatcircuitry capable of being integrated is made as an integrated circuit;and in the camera body, a switching circuit operated by a stored signaland manually set input circuit for manually set- 2 ting the exposuretime of the switching circuit are builtin and other integratablecircuitry is constructed as an integrated circuit.

Yet another object of the present invention is to provide an exposurecontrol system in which the exposure of the curtain shutter iscontrolled by a detecting circuit and a memory circuit constructed as anintegrated circuit, and a switching circuit is also constructed as aseparate integrated circuit.

SUMMARY OF THE INVENTION In order to attain the above-mentioned objects,the present invention relates to an exposure control system for aphotographic camera of the single lens reflex type wherein a housing,having a pentagonal prism, is attachable to and detachable from thecamera body, and in the housing a light receptive element is mounted forreceiving the scene light incident through the objective lens in thecamera body. A detecting circuit for detecting the current generated bythe light receptive element, a memory circuit for storing the detectedcurrent output, a generating circuit for generating currentcorresponding to the stored voltage of the memory circuit are built-inthe housing. All circuit capable of being integrated are-constructed asan integrated circuit. In the camera body a manual exposure time settingcircuit and a switching circuit operated by the output of the manualexposure setting circuit and/or the generating circuit for generatingcurrent corresponding to the stored voltage of the memory circuitarebuilt-in. Those circuits in the camera body that are capable of beingintegrated are also constructed as an integrated circuit. The switchingcircuit controls the exposure of the camera.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of the presentinvention;

FIG. 2 is a circuit diagram of an embodiment in accordance with'thepresent invention;

FIG. 3 is a longitudinal section of the essential portion of a camerashowing an arrangement of light receiving elements in accordance withthe present invention;

FIG. 4 is a diagram showing the relationship between the illuminance onthe light receiving plane of a light receptive element vs the output ofthe detecting circuit for variations of the film sensitivity and thediaphragm aperture setting;

FIG. 5 is a perspective view showing one example of an arrangement of acurtain shutter wherein the exposure of the curtainshutter is controlledby the exposure control system inaccordance with the present invention;

FIG. 6 is a perspective view showing the relationship between theopening curtain and the closing curtain of a curtain shutter and alsoshowing the exposure frame of the camera;

FIG. 7 is a diagram showing the movement of the opening curtain and theclosing curtain as a function of time;

FIG. 8 is a perspective view showing the arrangement of the essentialcomponents of one embodiment in accordance with the present invention;and

FIG. 9 is a block diagram showing the connection between the integratedcircuit mounted-in the camera body and the integrated circuit mounted inthe finder housing.

DETAILED DESCRIPTION OF THE INVENTION In the block diagram shown in FIG.1, block A is a detecting circuit for detecting the generated currentfrom a light receptive element in pentagonal prism container 2 and amemory circuit for storing the detected output. Light receptive element4 is mounted on roof plane 30 of pentagonal prism 3 mounted in finderhousing 2 attachable to and detachable from camera body 1 of a singlelens reflex camera, as shown in FIG. 3.

In FIG. 3, movable mirror 7 in the camera body is rotatably supported soas to be movable from the viewing position 7 (shown by the full line) tothe picture taking position 7 (shown by the broken line), and as wellknown the mirror is biased so as to be normally located in the viewingposition and is driven to the picture taking position in connection withthe release operation.

Therefore, when the release operation is effected, light receptiveelement 4 is shut off from the scene light an object passing throughobjective lens 5 and diaphragm 6. Accordingly, block A is required toinclude a detecting circuit for detecting the current generated by lightreceptive element 4 just before movable mirror 7 is driven by therelease operation from the viewing position; and a memory circuit forstoring the output information of the detecting circuit as well asinformation relating to the aperture of diaphragm 6 and the sensitivityof the film used.

Blocks B, C, D, E, and F, encircled by chain line G in FIG. 1, arecircuits built in camera body 1 in FIG. 3. Block B is an exposure timesetting circuit used for photographing in which the exposure time ismanually set instead of the output of block A and includes a constanttime delay circuit in which a capacitor and a resistance are connectedin series. By changing the resistance the time required for the chargingvoltage of the capacitor to reach a certain level is varied.

Block C is a change-over switch, for automatic exposure time control, toinput the output of either block A or B into block D, which corresponds,respectively, to automatic exposure time control or manual exposure timecontrol.

Block D is a differential switching circuit including a differentialamplifier circuit for effecting a switching operation when the output ofblock A or B, via block C, reaches a predetermined level.

Block E is a delay switching circuit including a delay circuit forproviding a certain minute time delay which is necessary because of thestructure of the curtain shutter; and a switching circuit for switchingthe output transistor after a predetermined time duration.

Block F is an electromagnet the excitation of which is shut off when theoutput transistor in block E is switched from the conductive state tothe nonconductive state, and releases the restraint of the shutterclosing curtain, the operation of which is described below.

The present invention is arranged as described above, and camera body 1is provided with a member by which the exposure time is manually set,and it is possible to use it as a camera having no automatic exposuretime control function and by mounting pentagonal prism housing 2, inblock A, thereon the exposure can be changed-over to automatic exposuretime control. Therefore, when carrying out only manual exposure timesetting photography it is understood that the camera can be used with apentagonal prism housing not provided with the circuitry of block A.

Block A is formed as an integrated circuit in pentagonal prism housing2, and in addition the control circuit in camera body 1 is also formedas an integrated circuit using the differential switching circuitportion of block D as a main body. In this manner, it is possible to reduce the number of terminals coming out of both integrated circuits andaccordingly the circuitry can be small-sized to be incorporated veryeasily in the camera.

The exposure control circuit of the electric shutter composed of theblocks mentioned above will be described hereinafter, with reference toFIG. 2. The portion surrounded by broken line A in FIG. 2 is the circuitry of block A within the pentagonal prism housing describedpreviously. Resistances R,, R and R, and transistor Tr, form a constantcurrent circuit. In order to keep the current from the collector oftransistor Tr, constant relative to the voltage fluctuations of powersource Ba and variations of ambient temperature, a circuit composed of atransistor, a diode, and a resistance may be added to the aforesaidconstant current circuit as is well known in the art.

The circuit connected to the collector of transistor Tr, comprises lightreceptive element 4 (the impedance of which is R,,) and resistance R,connected in series with each other; and resistances R, and R, connectedin series with each other and shunted across the light receptive elementR, and resistance R,. One terminal of shunted resistances R, and R, isconnected to the collector of transistor Tr and at connection point abetween light receiving element R and resistance R, a potentialproportional to the logarithm of the illuminance on the light receivingplane of light receptive element R is produced relative to groundpotential.

Variable resistance R,,, connected to the emitter of transistor Tr,,provides a signal representing the aperture setting of diaphragm 6 andthe film sensitivity. The base of transistor Tr, is connected to theconnection point between resistances R, and R Light receptive impedanceR, has an electrical equivalent of, for example, two photoconductiveelements connected in parallel with each other and the relation betweenthe illuminance on the light receiving plane of light receptive element4 and the electric potential at connection point a is as shown in FIG.4. The circuit in accordance with the present invention detects thebrightness-of an object with the diaphragm fully opened so that a presetaperture setting of the diaphragm is required together with the filmsensitivity as factors for the exposure time control. Variableresistance R, has a resistance which is linearly varied, and the filmsensitivity and the preset aperture settings are added by a well knownaddition mechanism not shown in the drawings and represented by theresistance of variable resistance R,,. The level of the electricpotential at connection point a shifts in accordance with change inresistance of resistance R, as shown by the broken lines in FIG. 4 For avariation of 1 EV of the film sensitivity or the preset aperture, thelevel of shift V is determined beforehand so as to be equal to avariation of lEV of the illuminance on the light receiving plane oflight receptive element 4. Resistances R and R, divide the power voltageto connection point c and the voltage at point 0 is fed as an input tothe differential amplifier circuit described below.

The electric potential at point a charges memory capacitor C, throughswitch SW (described below) and is charged to a voltage proportional tothe logarithm of the illuminance on the light receiving plane of lightreceptive element R The stored voltage of memory capacitor C isimpressed on the base of logarithm expansion transistor Tr and whenswitch SW is closed, the collector current flows to charge capacitor C,inserted in the collector circuit by a constant current proportional tothe illuminance on the light receiving plane of light receptive element4.

Switches SW, and SW are change-over switches for changing over betweenautomatic exposure time control (called hereinafter automatic exposurecontrol) and manually set time control (called hereinafter manualexposure control). These switches are mounted on the side of camera body1, and for automatic exposure control, change-over switches SW, and SWare connected to AUTO and for manual exposure they are connected to MAN.The circuit composed of switch SW and resistance R discharges theelectric potential of capacitor C or C Switches SW, and SW are both forautomatic exposure control and interlock with the release operation.Switch SW is opened just before movable mirror 7 (shown in FIG. 3)starts to turn to picture taking position 7' to disconnect the detectingcircuit from memory capacitor C Accordingly, the light rays to lightreceiving element 4 are blocked and the variation of electric potentialat point 0 shown in FIG. 2 has no effect upon memory capacitor C SwitchSW is closed simultaneously with the movement of the shutter effected bythe release operation to start to charge capacitor C and the timerequired for capacitor C to reach a predetermined charging voltage isthe exposure time.

The circuit in which capacitor C switch SW, and variable resistance Rare connected in series with one another forms an exposure time settingcircuit for manual exposure control, and switch SW performs the samefunction as switch SW for automatic exposure control. Variableresistance R in parallel with the aforesaid circuit, is a variableresistance determined in accordance with the aperture setting and thefilm sensitivity for manual exposure control.

The circuit composed of transistors Tr.,, Tr,,, Tr Tr-,, diodes D D andresistances R and R forms a differential amplifier circuit. The base oftransistor Tr, receives the charging voltage of capacitor C, or C andthe other transistor Tr in the case of automatic exposure control,receives the voltage at point e, where the power voltage is divided byresistances R and R and in the case of manual exposure control receivesthe voltage at point f of variable resistance R When the base potentialof transistor Tr, drops to coincide with the base potential oftransistor Tr transistor Tr,, is switched from non-conduction intoconduction and the collector potential drops to energize transistor TrTransistor Tr forms a switching circuit together with transistors Tn, TrTr and resistances R R and when transistor Tr, is switched intoconduction it reverses transistor Tr into non-conduction. The aforesaidswitching circuit and differential amplifier circuit form a differentialswitching circuit.

The collector and emitter of transistor Tr are connected to each otheracross capacitor C connected in series to variable set resistance RTherefore, when transistor Tr is switched into non-conduction, capacitorC id charged with a time constant determined by the resistance value ofresistance R and the capacity of capacitor C When the charging voltagereaches a predetermined voltage, transistor Tr is reversed fromnon-conduction into conduction to energize transistors Tr and TrTransistor Tr becomes non-conductive because the base current thereof iscut off. Electromagnet Mg, in the collector of output transistor Tr forretaining armature 21a of restraining lever 21 for rear curtain 9 in thecurtain shutter shown in FIG. 5, is blocked from being energized, andaccordingly the rear curtain starts to move to terminate the exposure.

Resistances R R and diodes D D connected to the emitter of transistor Trform a circuit for compensating the operation of transistor Tr forchanges in temperature and voltage fluctuations of power source. DiodesD D and D connected to transistor Tr across the collector and emitterthereof, absorb the counter-electromotive force induced in electromagnetMg, and resistances 21 and 22 regulate the base current of transistorsTr and Tr The following is a description of the operation of theautomatic exposure control formed as described above. In this case,change-over switches SW, and SW8 are connected to the AUTO side of theircontacts, switches SW and SW, are closed, and switches SW and SW, areopened. But the opening/closing of switch SW is unrelated to theoperation in this case.

Before taking a picture the resistance of variable resistance R isdetermined by the setting of the diaphragm aperture and the sensitivityof the film used; and power switch SW is, for example, open, and whenshutter button 11 of the camera is depressed, switch SW is closed as itis interlocked with shutter button 1 l. Thereby, the electric circuit isenergized, however, capacitor C has been short-circuited by closedswitch SW, and accordingly the base potential of transistor Tr, in thedifferential amplifier circuit is lower than that of transistor TrTherefore, transistor Tr is nonconductive. As a result, transistors TrTr,, and Tr are non-conductive, transistor Tr, is energized, andcapacitor C, in the differential switching circuit is shortcircuited.Output transistor Tr is energized to excite electromagnetic Mg and thedriving of rear curtain 8 of the curtain shutter (shown in FIG. 5) ischecked. That is, FIG. 5 shows the essential portion of the mechanicalstructure of the curtain shutter in accordance with the presentinvention wherein the shutter is cocked. In FIG. 5, the image forminglight ray of an object passing through photographic lens 5 and diaphragm6 is blocked by shutter front curtain 8. When front curtain 8 drives inthe direction shown by arrow 10, the exposure is started, and after apredetermined time rear curtain 9 drives in the direction shown by arrow10 and the exposure is terminated. Upon depressing shutter button 1 lthe restraint of the front curtain restraining member (not shown in thedrawing) is released, and at the same time the engagement of pin 13 ofwinding gear 12 and pin 15 of gear 14 is disconnected. Thereby, therestraint of gear 16 is released, and opening gear 17, meshed with gear16, is driven in the direction shown by arrow 10 by front curtaintake-up shaft 18. Whereas, as to rear curtain 9, with electromagnetic Mgexcited as described above, armature 21a is attracted against spring 22and closing restraining lever 21 engages with pin 20 of gear 19 meshedwith closing gear 23 to check the rotation of gear 19. Accordingly, rearcurtain 9 is checked against being driven. And, when electromagnetic Mgis demagnetized by the switching operation of the differential switchingcircuit described above, the engagement of closing curtain restraininglever 21 and pin 20 is disconnected, and gear 19 rotates and rearcurtain 9 starts to drive to shut off the exposure.

By the process of further depressing shutter button 11, switches SW, andSW, in FIG. 2 are opened and then switch SW is closed simultaneouslywith starting movement of front curtain 8, and collector current 10,,proportionately expanded with respect to the voltage between the baseand emitter of transistor Tr flows to charge capacitor C The electricpotential at point d on one end of capacitor C, drops and accordinglythe base potential of transistor Tr, in the differential amplifiercircuit drops, and when that base potential drops lower than theelectric potential at point c set by resistances R, and R namely, thebase potential of transistor Tr both transistors Tr, and Tr, arereversed. Transistor Tr,

becomes conductive, transistor Tr becomes non-- conductive, andcapacitor C starts to charge by the current flowing through variable setresistance R The time between when the front curtain starts to drive andwhen transistor Tr is switched into nonconduction is the exposure timeautomatically controlled by the detecting circuit and the differentialswitching circuit. However, in the present invention the drivingmovement of the rear curtain is formed to start a specific time laterthan the time when transistor 11 became non-conductive. The reason willbe described hereinafter.

FIG. 6 shows the camera opening frame 25 and the relation between bothfront and rear curtains 8 and 9 at the time when the shutter is cockedas in FIG. 5. In such a curtain shutter having two curtains, in generalin order to prevent light from leaking during winding, a predeterminedoverlap such as the portion shown by numeral 26 in FIG. 6 is formedbetween front curtain 8 and rear curtain 9. As a result, both curtainshave driving movements as shown in FIG. 7. In FIG. 7, the abscissa showsthe time interval 1 from the driving start of the front curtain, and theordinate shows the moving position S of the curtain during a certaintime interval. S, indicates that rear curtain 9 starts to be driven froma position closer to the side of take-up shaft 24 than front curtain 8by as much as the width 26 of the overlap of both curtains. S, and Sindicate both ends of a film picture plane exposed over opening frame 25of the camera. Curve 27 indicates the displacement characteristic offront curtain 8 as a function of time and curves 28, 29, 30, 31, and 32indicate respective movement characteristics of rear curtain 9 which isstarted at times t t,, t t or t, seconds subsequent to the driving startof front curtain 8. The fact that the slope of every curve of bothcurtains is small just after being started is due to the force ofinertia. The transverse interval between the driving curves 27 and theother curves 28 to 32 on the film picture plane (between S, and 8,) arethe respective exposure times.

Thus, when the movement of rear curtain 9 is started a time, t after thedriving of front curtain 8 is started, both curves 27 and 28 are fullyoverlapped between S, and 8,. THis fact indicates that even though thedriving of rear curtain 9 is started a time, t after the driving offront curtain is started, the relative cocked positions of the screensare such that the exposure time substantially effected is zero. Thisfact means that also between driving curve 27 and the other drivingcurves 29 to 32 the exposure time is shortened relative to therespective starting times, t, to t,, of rear curtain 9. That is to say,in general, provided the exposure time of a film is T and the startingtime interval between the curtains is Ts, the relationship, Ts T T isestablished.

As described above, time t is based on the overlap of front and rearcurtains 8 and 9 and specifically by the amount of overlap thereof,which is an inherent constant for every curtain shutter. t is in generalfrom 4/ 1000 to 5/ 1000 seconds and from 4 to 5 times as high as thehighest speed I] 1000 second of the shutter, as determined frommeasurements of common curtain shutters. Therefore, sufficientcompensation of the exposure error due to such a time t is veryimportant for increasing the precision of the shutter speed.

In the present invention, a delay switching circuit to compensate fortime t is provided on the output side of the differential switchingcircuit. This is the circuit from variable set resistance R andcapacitor C to transistor Tr The impedance of variable resistance R isproperly set for a particular camera and a delayed operation timeequivalent to t for the switching time of transistor Tr is provided,after which output transistor Tr operates electromagnet Mg.

Further, in the case of manual exposure control, by connectingchange-over switches SW, and SW, to contact MAN and optionally settingthe impedance of variable resistance R,,, the shutter speed setting isset. After the closing of switch SW,, upon depressing the shutter buttonswitch SW, is first opened and then switch SW is closed. And thus,capacitor C is charged, and when the electric potential at connectionpoint e drops lower than that of sliding terminal f of variableresistance R (for converting the film sensitivity and the diaphragmaperture), the conduction of transistors Tr, and Tr, in the differentialamplifier circuit is reversed and transistor Tr, is made conductive.Thereafter, the same operations as in automatic exposure control arecarried out.

The primary purpose of the present invention is to integrate the circuitin FIG. 2 to facilitate its incorporation in a camera. The chip of anintegrated circuit itself is very small-sized, but the terminals comingout of the chip become numerous and accordingly the space therefor isincreased as a matter of course. If the entire circuit shown in FIG. 2is integrated on one base plate, the number of terminals for theintegrated circuit would be 26, and incorporating such an integratedcircuit would require increasing the capacity of the camera.

Therefore, in the present invention, the circuits are divided betweenpentagonal prism housing 2 and camera body 1, and pentagonal prismhousing 2 is interchangeably attached to and detached from the camerabody. In pentagonal prism container 2 there are mounted light receptiveelement 4; the circuit for charging with a constant current thecapacitor for controlling the exposure time to a value determined by theilluminance on the light receiving surface of light receptive element 4,the aperture setting, and the sensitivity of the film used; and thememory circuit. The integrated circuit thereof is composed oftransistors, diodes, and small resistances. In camera body 1 there aremounted the exposure time setting circuit for manually setting theexposure time; a change-over switch for changing over the output of thememory circuit and the exposure time setting circuit; and the switchingcircuit including the differential amplifier circuit to which the memorycircuit or the exposure time setting circuit is connected via thechange-over switch. These circuits are also integrated. By usingintegrated circuits and dividing the circuits as indicated above, thenumber of terminals is reduced to under 14 and the respective chips aresmall-sized so that they are respectively incorporated into pentagonalprism housing 2 and camera body 1 with ease.

The arrangement of the respective circuits incorporated in camera body 1and pentagonal prism housing 2 is shown in FIG. 8. Reference numeral 33denotes an opening formed on the central portion of the top surface ofcamera body 1. In opening 33 interchangeable pentagonal prism housing 2is fitted, and by pin 34, projecting on the opposite side of eyepiece 36of pentagonal prism housing 2, and lock member 35, formed on the sidewall of opening 33, pentagonal prism housing 2 is fixed in a definiteposition in opening 33. And, when movable mirror 7 is located in theviewing position, the image of the scene light passing through objectivelens and diaphragm 6 from an object is observed in eyepiece 36.

Numeral 37 denotes a winding lever formed on camera body 1, and 38 afilm rewinding member having foldable rewinding lever 39, and therewinding shaft extends inwardly from the center of rewinding member 38into camera body 1. Numeral 40 denotes an exposure time setting dial,and 41 an operation member for operating change-over switches SW and SW,described above.

On the top surface of pentagonal prism housing 2 film sensitivitysetting dial 42 and exposure time setting dial 43 are formed, and on theside wall on which eyepiece 36 is formed there are also provided switch44 for opening/closingthe power source and operation member 45 forscreening eyepiece 36 to shut off the light rays coming from eyepiece 36into the pentagonal prism.

In pentagonal prism housing 2 there is formed a flexible base plate 48with printed conductors 47 to which the terminals of integrated circuitA" and the terminals of the other circuits which are not integratableare connected. For example, at portion 49 of base plate 48 conductor 47forms exposed contact portion 50, and printed conductors 47 are coatedwith an insulating film of the same substance as the base plate. Numeral55 denotes a meter.

On the slanting lower portion of rewinding member 38 in camera body 1,integrated circuit G", composed of the manual exposure time settingcircuit and the differential switching circuit including thedifferential amplifier circuit, is mounted. On base plate 51 terminals52 of the integrated circuit and of the non-integratable circuits areconnected to elastic contact pieces 53 made of metal and the ends ofcontact pieces 53 are inserted into opening 33 from window 54formed onthe side wall of opening 33.

Thus, when pentagonal prism housing 2 is mounted in the proper positionin opening 33, elastic contact pieces 53-are electrically connected toprinted conductors 47 of flexible base plate 48 respectively byconnection contact 50, and the circuitshown in FIG. 2 is set up.

What is claimed is:

1. An exposure control system for a single lens reflex cameracomprising:

a camera body including reflecting means movable between a viewingposition and a picture taking position;

a housing attachable to said camera body and including:

a light receptive element for generating a signal in accordance with theincident light thereon;

said reflecting means reflecting light passing through the objectivelens of the camera to said light receptive element and a viewfinder insaid viewing position;

means for detecting said signal and generating an output signal;

means for storing said output signal;

an integrated circuit comprising elements from said means for detectingand said means for storing, said integrated circuit including firstterminals; and

non-integrated circuitry including the other elements from said meansfor detecting and said means for storing and having second terminals;

and at least one of said second terminals connecting with at least oneof said first terminals;

said camera body further including:

a circuit for manually setting exposure time;

switching means for changing between manual and automatic time-exposuresettings and connected to one of said first terminals connected to saidmeans for storing;

switching circuit means connected to said means for switching;

means actuated by said switching circuit means for terminating exposure;

a second integrated circuit including elements of said circuit formanually setting exposure time and said switching circuit means, saidsecond integrated circuit including third terminals; and

second non-integrated circuitry including the other elements of saidmeans for manually setting exposure time and said switching circuitmeans, and including fourth terminals, and at least one of said fourthterminals connecting with at least one of said third terminals.

2. An exposure control system for a single lens reflex camera as inclaim 1 wherein with said housing attached to said camera bodyconnections are established between said first and said secondterminals, and said third and said fourth terminals.

3. An exposure control system for a single lens reflex camera as inclaim 2 wherein:

said means for detecting includes means for generating constant current,a first transistor, a first resistance connected in series with saidlight receptive element, a divided resistance connected in parallel withsaid light receptive element and said first resistance andinterconnecting said means for generating constant current with thecollector of said first transistor, the base of said first transistor isconnected to the junction of said divided resistance, a variableresistance connected to the emitter of said firsttransistor and having aresistance varying in accordance with the sensitivity of the film andthe diaphragm aperture setting, and an output terminal connected to thejunction of said light receptive el ement and said first resistance;

said means for-storing includes a capacitor, a first normally closedswitch interconnecting said capacitor with said. output signal, saidfirst switch is opened prior to the movement of said movable junctionbetween said resistance and said second means from said viewing positionto said picture capacitor is connected to the output of saidswitchtaking position with the camera release operation; ing circuitmeans;

and a second transistor having a base connected to the whereby thevariation in the voltage produced by said 5 junction of said resistanceand said second capacioutput signal from a one volt variation acrosssaid tor, said means for terminating exposure is driven variableresistance is the same variation in the voltby said second transistor;and

age produced by said output signal from a one volt said secondresistance is set at a value whereby the variation produced by the lightradiation on the error in exposure time introduced by said overlightreceiving plane of said light receptive elelapped opening and closingcurtains is compenment. sated.

4. An exposure control system for a single lens reflex 5. An exposurecontrol system for a single lens reflex camera as in claim 2 whereinsaid camera includes camera as in claim 2 wherein either one of saidfirst and opening and closing curtains cocked in overlapping resecondterminals, and said third and fourth terminals is lationship and whereinsaid camera body further ina flexible contact element; and the other ofsaid first cludes: and second terminals, and said third and fourthtermia constant time delay circuit including a series connals is printedon a flexible insulating base plate.

nected second resistance and second capacitor, the

1. An exposure control system for a single lens reflex cameracomprising: a camera body including reflecting means movable between aviewing position and a picture taking position; a housing attachable tosaid camera body and including: a light receptive element for generatinga signal in accordance with the incident light thereon; said reflectingmeans reflecting light passing through the objective lens of the camerato said light receptive element and a viewfinder in said viewingposition; means for detecting said signal and generating an outputsignal; means for storing said output signal; an integrated circuitcomprising elements from said means for detecting and said means forstoring, said integrated circuit including first terminals; andnon-integrated circuitry including the other elements from said meansfor detecting and said means for storing and having second terminals;and at least one of said second terminals connecting with at least oneof said first terminals; said camera body further including: a circuitfor manually setting exposure time; switching means for changing betweenmanual and automatic timeexposure settings and connected to one of saidfirst terminals connected to said means for storing; switching circuitmeans connected to said means for switching; means actuated by saidswitching circuit means for terminating exposure; a second integratedcircuit including elements of said circuit for manually setting exposuretime and said switching circuit means, said second integrated circuitincluding third terminals; and second non-integrated circuitry includingthe other elements of said mEans for manually setting exposure time andsaid switching circuit means, and including fourth terminals, and atleast one of said fourth terminals connecting with at least one of saidthird terminals.
 2. An exposure control system for a single lens reflexcamera as in claim 1 wherein with said housing attached to said camerabody connections are established between said first and said secondterminals, and said third and said fourth terminals.
 3. An exposurecontrol system for a single lens reflex camera as in claim 2 wherein:said means for detecting includes means for generating constant current,a first transistor, a first resistance connected in series with saidlight receptive element, a divided resistance connected in parallel withsaid light receptive element and said first resistance andinterconnecting said means for generating constant current with thecollector of said first transistor, the base of said first transistor isconnected to the junction of said divided resistance, a variableresistance connected to the emitter of said first transistor and havinga resistance varying in accordance with the sensitivity of the film andthe diaphragm aperture setting, and an output terminal connected to thejunction of said light receptive element and said first resistance; saidmeans for storing includes a capacitor, a first normally closed switchinterconnecting said capacitor with said output signal, said firstswitch is opened prior to the movement of said movable means from saidviewing position to said picture taking position with the camera releaseoperation; and whereby the variation in the voltage produced by saidoutput signal from a one volt variation across said variable resistanceis the same variation in the voltage produced by said output signal froma one volt variation produced by the light radiation on the lightreceiving plane of said light receptive element.
 4. An exposure controlsystem for a single lens reflex camera as in claim 2 wherein said cameraincludes opening and closing curtains cocked in overlapping relationshipand wherein said camera body further includes: a constant time delaycircuit including a series connected second resistance and secondcapacitor, the junction between said resistance and said secondcapacitor is connected to the output of said switching circuit means; asecond transistor having a base connected to the junction of saidresistance and said second capacitor, said means for terminatingexposure is driven by said second transistor; and said second resistanceis set at a value whereby the error in exposure time introduced by saidoverlapped opening and closing curtains is compensated.
 5. An exposurecontrol system for a single lens reflex camera as in claim 2 whereineither one of said first and second terminals, and said third and fourthterminals is a flexible contact element; and the other of said first andsecond terminals, and said third and fourth terminals is printed on aflexible insulating base plate.